Variable high intensity infrared heater

ABSTRACT

A radiant heating system having a housing for holding a plurality of gas burners with a ceramic burner element that emits infrared rays after becoming hot. A controller is used for selectively controlling at least one valve to restrict the gas flow to the individual burners. A method is shown for radiating heat from a gas burner in response to a thermostat by controlling the gas flow to individual burners with electronic valves located in a gas supply line and selectively shutting off the gas flow to each burner.

FIELD OF THE INVENTION

[0001] This invention relates to an apparatus and method for heating anenclosed space with a variable high intensity infrared heater.

BACKGROUND OF THE INVENTION

[0002] High intensity gas-fired infrared heaters are typically used inlarge commercial or industrial settings. A gas heater burns natural gas,propane or other similar combustible gases to heat a porous ceramicplate. The ceramic plate turns red hot and emits infrared energy waves.Such heaters often include reflectors to broadly reflect the energywaves. Such high intensity infrared heaters generally operate at fullcapacity when not in an off condition. This operating condition resultsin the burner constantly cycling between its on condition and its offcondition thus making it difficult to control heating levels.

SUMMARY OF THE INVENTION

[0003] A radiant heating system having a housing for holding a pluralityof gas burners. The fuel used in these burners is typically natural gasor propane gas. The gas burners each have a plenum for mixing the gaswith combustion air, a ceramic burner element that emits infrared raysafter becoming hot, a controller for selectively controlling the gasburners, a common rail gas line for supplying the gas from an inlet lineto the plurality of burners, and at least one valve positioned in thecommon rail gas line to prevent gas from flowing to burners locateddownstream from the valve. The valves for controlling the gas flow tothe individual burners are positioned downstream of the first burner andprior to the inlet of each succeeding burner so that the downstreamburners can be individually turned on and off by the controller. Acontroller for the gas heater provides a room temperature set by athermostat. The controller controls the temperature between a lowerthreshold temperature and an upper threshold temperature by controllingthe numbers of individual gas burners operating. A control algorithm isdesigned to heat up a space as quickly as possible by turning all theburners on, while minimizing the overshoot and undershoot of the setpoint temperature by selectively reducing the number of burnersoperating as the room temperature fluctuates between the lower thresholdand the set point temperature. The gas burner has a 100 percent safetyshut-off feature and is powered by a 24-volt electrical source. Directspark ignition with a spark electrode is used to ignite the fuel. Theburner does not require a pilot to be lit continually for operation. Theburner uses a flame sensing electrode for determining if the burner isoperational.

[0004] A method for radiating heat comprising operating a gas burner inresponse to a thermostat, controlling the gas flow to individual burnerswith electronic valves located in a gas supply line by selectivelyshutting off the gas flow delivered to individual burners, generatinginfrared rays from a hot ceramic burner surface, and reflecting theradiated infrared rays from a reflector in a desired direction.

[0005] Other applications of the present invention will become apparentto those skilled in the art when the following description of the bestmode contemplated for practicing the invention is read in conjunctionwith the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0006] The description herein makes reference to the accompanyingdrawings wherein like reference numerals refer to like parts throughoutthe several views, and wherein:

[0007]FIG. 1 shows a front view of a variable high intensity infraredheater;

[0008]FIG. 2 shows a rear view of the variable high intensity infraredheater;

[0009]FIG. 3 is a control diagram of the variable intensity infraredheater; and

[0010]FIG. 4 is a graph of temperature versus time showing less wastedenergy with a multi-stage system than with a single stage system.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0011] High intensity gas-fired infrared heaters are typically eithercontrolled in the on or off position so that the burner elements areeither all firing or all off. An improvement to the heater allows one ormore burner elements to be selectively shut off so that a set pointtemperature can be controlled more precisely by minimizing overshoot andundershoot of the desired temperature.

[0012] With reference to FIGS. 1 and 2, there is shown a high-intensityradiant heating system 10 having a housing 12 for holding a first burner16 and a second burner 18. This preferred embodiment shows two burners,but it should be understood that there is no limit as to the maximumnumber of burners in this apparatus, e.g., 3, 4, 5, 6, . . . Ceramicburner elements 17, 19 are heated until they are red hot so thatinfrared energy waves are generated therefrom. A reflector 14 reflectsthe infrared rays emitted from burners 16, 18 in a desired direction toprovide heat. A spark electrode ignitor 27 is used to initiatecombustion of the fuel. A combination power supply and controller 28includes logic for ignition detection control and operational controlover the various components on the heating system 10. After power isapplied to an ignition detection controller (IDC) 31, a delay ofpreferably fifteen seconds occurs before a spark is developed at theelectrode 27 and a gas regulator valve 22 opens allowing gas to flow tothe burners 16, 18. A flame sensing electrode 29 is used to determinewhen combustion has begun and to signal the IDC 31 to power down thespark electrode ignitor 27. The flame sensing electrode 29 will signalthe IDC 31 to power up the spark electrode ignitor 27 when a flameoutcondition is detected. The spark electrode ignitor 27 generally beginsfiring within 0.8 seconds of a flameout condition.

[0013] Heater 10 has a gas inlet line 20 for providing gas from anexternal source to the burners 16,18. Gas, preferably natural gas orpropane, passes through a regulator valve 22. Regulator valve 22 iscapable of shutting off the gas flow to burners 16, 18 and providing afixed amount of gas to burners 16 and 18. After passing throughregulator valve 22, the gas enters a common rail gas line 24 fordistribution to individual burners 16, 18. A trunk line 30 tees intocommon rail 24 to deliver gas to burner 16 while a second trunk line 32provides gas from common rail 24 to burner 18. It is understood that ifmore than two burners are provided, each would be provided gas by atrunk line connected to the common rail 24. A solenoid valve 26 can beinstalled in common rail 24 or in trunk line 32 downstream of burner 16.Solenoid valve 26 prevents gas from traveling downstream therefrom thuspreventing gas from flowing to burner 18.

[0014] Spark electrode ignitor 27 provides a spark to start combustionin burner 16 which, if gas is flowing to burner 18, causes burner 18 toignite by a flame transfer from burner 16. A combination power supplyand controller 28 controls power to the solenoid valve 26, spark ignitorelectrode 27, regulator valve 22, and the flame sensing electrode 29.Solenoid valve 26 is operable to selectively prevent gas from flowingdownstream to burner 18 thus selectively allowing only burner 16 tooperate.

[0015] Referring now to FIG. 3, a schematic diagram illustrates a methodfor controlling the variable high intensity infrared heater 10. Thecontrol sequence starts with determining if the thermostat set pointtemperature is below a first (lowest) threshold in query 52. If theanswer to query 52 is yes, then the controller turns all the burners onin 54. Power is applied to the IDC 31 and, fifteen seconds after poweris applied, a spark is developed at the spark electrode ignitor 27 andthe regulator valve 22 opens allowing gas to flow to the burners 16, 18.The spark electrode ignitor 27 begins ignition and an electrical currentbegins flowing from the flame sensing electrode 29 through the flame toa ground to determine when to shut off the spark. The IDC 31 senses thecurrent and turns off the spark once the flame has taken hold and thegas continues to flow through the regulator valve 22. If the burners 16,18 have a flame outage detected by the flame sensing electrode 29, theIDC 31 responds by initiating sparking within preferably 0.8 seconds. Apreferred fifteen second ignition period initiates the attempt torelight the burners 16, 18. If the flame is reestablished, then normaloperation resumes. If the burners 16, 18 do not light after the firsttry, an interpurge sequence preferably occurs between trials beforeattempting to relight the burners 16, 18. If the burners 16, 18 fail tolight after the third trial, the IDC 31 will de-energize the regulatorvalve 22 and go into lock-out mode. Lock-out recovery requires thethermostat 40 to be reset below ambient temperature or the electricalpower supply to be shut off for five seconds. If the answer to query 52is no, then the controller checks the thermostat to see if thetemperature is below a second (lower) threshold in query 56. If theanswer to query 56 is yes, then the controller 28 turns one burner on in58. If the answer to query 56 is no, then the controller loops back to50 and turns all the burners off. The controller loops back to query 52after turning all burners on in 54 or turning one burner on in 58 todetermine if the temperature is below a first (lowest) threshold. Thecontroller 28 will continue looping through the algorithm until heater10 is manually turned off.

[0016] The controller 28 allows the heater 10 to operate with a variablenumber of burners to control the room temperature within a second(lower) threshold temperature and the set point temperature whileminimizing the on and off fluctuations of the heater system 10. Thecontrol system is designed to heat a location as quickly as possiblewhile minimizing overshoot and undershoot of the set point temperatureby varying the number of burners firing. For example, starting in thequery 52, if set point temperature is 72° F., the first (lowest)threshold could be 60° F., and a room temperature is 50° F., then allthe burners will be turned on at 54. As the room temperature begins towarm up, the controller 28 continues to measure the room temperature viathe thermostat 40 to determine if the temperature is below the firstthreshold temperature. If the answer is no, then the controller willcheck whether the temperature is below a second (lower) threshold in 56,for example 70° F. If the room temperature is above 70° F. in query 56,then all of the burners are turned off in 50. If the room temperature inquery 56 is less than 70° F., but greater than 60° F., then thecontroller will turn one burner on in 58. If the room temperature fallsbelow the first threshold 60° F. in query 52 then all of the burners areturned on in 54. The control algorithm will continue to loop throughthis method until the heating system 10 is manually shut off.

[0017] Referring now to FIG. 4, a plot 80 of temperature versus time isshown comparing a single stage system 82 with a multi-stage system 84.The plot 80 shows that with the multi-stage system 84 the overshoot andundershoot of the temperature set point is greatly reduced compared withthat of the single stage system 82. Overshoot peaks 86 show the amountof wasted energy that the single stage system 82 produces relative tothe multi-stage system 84. The multi-stage system 84 not only saves onenergy usage, but, since the undershoot and overshoot of the temperatureset point is minimized, the comfort level is improved for occupants inthe room.

[0018] While the invention has been described in connection with what ispresently considered to be the most practical and preferred embodiment,it is to be understood that the invention is not to be limited to thedisclosed embodiments but, on the contrary, is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the appended claims, which scope is to be accorded the broadestinterpretation so as to encompass all such modifications and equivalentstructures as is permitted under the law.

What is claimed is:
 1. A radiant heating system comprising: a housingfor holding a plurality of gas burners, the burners having a plenum formixing gas with air prior to combustion of the gas and air mixture; agas line having a first end and a second end for supplying gas to theburners; and at least one valve positioned in the line to selectivelyprevent gas from flowing to burners located downstream from the valve.2. The radiant heating system of claim 1, wherein the gas line is acommon rail.
 3. The radiant heating system of claim 1 furthercomprising: a reflector attached to the housing and positioned aroundthe burners for reflecting the infrared rays in a desired direction. 4.The radiant heating system of claim 1, wherein the valve is a solenoidvalve.
 5. The radiant heating system of claim 1 further comprising: agas regulator valve connected between the gas inlet line and the gascommon rail line for providing a fixed amount of the gas flow to thecommon rail.
 6. The radiant heating system of claim 1 furthercomprising: an ignitor located on at least one of the burners forigniting the air and gas mixture.
 7. The radiant heating system of claim6 further comprising: a power supply for supplying power to thecontroller, the solenoid valve, the ignitor, and the regulator valve. 8.The radiant heating system of claim 1 wherein the burner element is madeof ceramic material.
 9. The radiant heating system of claim 1 furthercomprising: a thermostat for signaling the controller to start and stopindividual burners when heat is required.
 10. A radiant heating systemcomprising: a controller for a gas heater to provide a set point roomtemperature within a lower threshold and an upper threshold bycontrolling gas flow to individual burners based on a control algorithm;the control algorithm being designed to heat a location as quickly aspossible while minimizing overshoot and undershoot of the set pointtemperature by firing all the burners in a cold condition andselectively reducing the number of burners operating once the roomtemperature is within a predetermined temperature of the set pointtemperature; the control algorithm being designed to selectively firethe individual burners to keep the temperature between the lowerthreshold and the set point temperature.
 11. A method for radiating heatcomprising: operating a gas burner in response to a thermostat;controlling gas flow to individual burners with electronic valveslocated in a gas supply line by selectively shutting off the gas flowdelivered to the individual burners; generating infrared rays from a hotceramic burner surface; and reflecting the radiated infrared rays from areflector in a desired direction.
 12. The method claim 11 furthercomprising: regulating gas flow entering into a common rail line. 13.The method claim 11 further comprising: igniting a gas and air mixturein a plenum of at least one of the burners for generating heatedcombustion products.
 14. The method claim 11 further comprising:supplying power to the controller, the solenoid valve, the ignitor, andthe regulator valve for operation of the gas burner.
 15. The methodclaim 11 further comprising: signaling the controller with a thermostatto start and stop individual burners for providing a desired amount ofheat.
 16. An apparatus for radiating heat comprising: means foroperating a gas burner in response to a thermostat; means forcontrolling gas flow to individual burners with electronic valveslocated in a gas supply line by selectively shutting off the gas flowdelivered to each burner; means for generating infrared rays from a hotceramic burner surface; and means for reflecting the radiated infraredrays from a reflector in a desired direction.
 17. The apparatus claim 16further comprising: means for regulating gas flow entering into a commonrail line.
 18. The apparatus claim 16 further comprising: means forigniting a gas and air mixture in a plenum of at least one of theburners for generating heated combustion products.
 19. The apparatusclaim 16 further comprising: means for supplying power to thecontroller, the solenoid valve, the ignitor, and the regulator valverequired for operation of the gas burner.
 20. The apparatus claim 16further comprising: signaling the controller with a thermostat to startand stop individual burners for providing a desired amount of heat.